Beavers

At one time there were an estimated 100 to 200 million of these animals across North America from Atlantic to Pacific north of the desert southwest and south of the Arctic tundra. Hunting and trapping reduced their numbers until they almost became extinct. Today there are between 10 and 15 million of North America’s largest rodent. They are the North American beavers (Castor canadensis) also known as Canadian beavers, or simply beavers.

Beavers spend most of their time in the water where they find protection from predators. They secrete an oily substance to waterproof their fur which consists of a fine inner layer and a coarse outer layer. They also have a thick fat layer under their skin for insulation from the cold water. Their back paws are webbed for swimming, and their unwebbed front paws have sharp claws for grasping sticks. They use their flat tail to slap the water as a danger signal. Nictitating membranes protect their eyes while allowing them to see underwater. Their ears and nostrils close while they are underwater and they can hold their breath for up to 15 minutes.

The main thing most people know about beavers is that they chew down trees with their special incisor teeth and they use those trees to build dams. Those dams create a pond where the beavers construct a lodge for shelter and protection. The only entrance to the lodge is underwater. The pond is valuable to more than just the beavers. It provides a habitat for waterfowl, fish, and other aquatic animals. Beaver dams also help reduce flooding and soil erosion. A beaver dam spotted on satellite imagery in Canada is more than half-a-mile (850 meters) long—more than twice the length of Hoover Dam in Nevada.

Beavers live on a diet of leaves and bark. In the fall they collect tree branches and preserve them underwater for winter food. They often stick the chewed-off end of the branches into the mud at the bottom of the pond. The branches may extend above the water where they collect snow and provide an insulated area where ice doesn’t form, and where the beaver can emerge.